


Sex or Die

by LA_Peach



Category: Undertale (Video Game)
Genre: Alphyne, Anal Sex, Double Penetration, Dubious Consent, Exhibitionism, F/F, F/M, NO FONTCEST, Papriel - Freeform, Please See Notes, Sex drugs, Vaginal Sex
Language: English
Status: Completed
Published: 2020-07-09
Updated: 2020-07-09
Packaged: 2021-03-05 05:20:16
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,257
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25169092
Author URL: https://archiveofourown.org/users/LA_Peach/pseuds/LA_Peach
Summary: Sans and Papyrus have been tricked into ingesting a by product of the Determination Extractor. Alphys knows the effects of the 'drug', the boys need some good old fashioned lady love or they will die.
Relationships: Alphys/Undyne (Undertale), Sans/Toriel/Papyrus (Undertale)
Kudos: 8





	Sex or Die

**Author's Note:**

> I have debated posting this one for a while, as it wasn't until long, LONG after I had finished writing it that I realized someone may misinterpret my intent. So, in the interest of tagging this properly and making sure that you can cater to your own interest, I chose 'not to use archive warnings' because this is not a rape/non-con story, but to many this may very well fall into uncomfortable territory, thus the 'dubious consent' tag. Papyrus is unconscious at the beginning, yes. But my intent is to have nothing more than a silly, friendly, kinky story. 
> 
> This fic is actually quite old and was one of the first I'd ever written. My writing style is different now, please keep that in mind if you are used to my newer work.
> 
> I wrote this as a sequel to my NSFW comic, The Ceremony, therefore it has a bit of a darker tone. In that story, Asgore has set up a yearly 'ceremony' where the monster congregate to breed. This is how he finds out that Sans' children are half human, (that Sans himself is actually human, no I have no idea how that happened) with powerful souls, and is on a weird mission to breed more powerful souls for his own gain. This is his attempt outside of the Ceremony to produce more souls.

_Knock knock knock_

The incessant, urgent noise sounded from the door. It had started out strong but as Toriel descended the stairs she swore it was getting weaker. The night was late and only sheer luck saw her still awake, otherwise she would have never heard the visitor at her door. Upstairs, her earlier visitor politely waited for her to return.

The knocking had stopped. At first, Toriel had been somewhat hopeful, excited. Sans often dropped by later at night, when the two of them could share a quite evening together. But this was much later than usual.

She opened the door and she grinned, noticing Sans right away in his blue hoodie and impish smile. But the smiled seemed strained…one of his eyes had gone dark, the other glimmering faintly indicating prolonged use of his magic. He was panting and his legs were shaking. He held his brother’s arm over his shoulder like Papyrus was drunk.  
But Toriel could tell that something else was seriously wrong. Papyrus was hardly moving, his breathing shallow and strained, his eyes closed. Somehow, along the brothers’ journey, Papyrus had lost both his boots and his briefs and was sporting the hardest, largest erection she had ever seen on a skeleton.

Sans was glowing through his shorts.

All of this she observed in mere seconds. Confused and concerned, she looked to her lover for an explanation. “Hey babe. Sorry about this. Can you take Paps? I can’t move my legs.”

She did so, careful not to touch the tall skeleton’s throbbing member, her cheeks flushed red, slinging his other arm across her shoulder and lifting him off of Sans.

Papyrus was not heavy, at least, not for Toriel but Sans collapsed to his knees.

“Sans, what’s wrong? What’s happened to you two?” 

“I’ll explained upstairs.”

“But Alphys is visiting, she’s drinking tea on my couch.”

“Heh. That’s lucky. Maybe she can help.”

Alphys wrung her hands nervously, trying not to stare at Papyrus on the couch. Sans was trying to explain what had happened to them, although he seemed to be having trouble remembering some of it. He kept his hands planted firmly beside himself, clenched in fists, as if struggling with some inner demons.

“There was a party? Ugh.” He panted, closed his eyes, and tried to think past the fog in his head. “Food. Lots of food.” He glanced at Toriel guiltily, “I remember lots of lady monsters.”

Alphys hunched her shoulders and tried to disappear into her lab coat. She knew what had happened here, at least she had a pretty good idea. “W-were there any other male monsters there?”

Sans put a hand to his head, trying to think. “Um… no. We were the only… wait. Asgore. Asgore was there, in the beginning.”

“Asgore?”

“He gave me some ketchup. I think he left after that.”

“What happened to Papyrus?”

Toriel was sure San’s eye seemed a bit dimmer than before. And Papyrus? His breathing was slowing down. Whatever had happened to them… they were running out of time. Sans was having more and more trouble finding the words. It was obvious that he was exhausted; soon he’d be as catatonic as his brother.

Sans closed his other eye. “Spaghetti,” he breathed. “He ate a lot of spaghetti.” He leaned his head back on the couch, nearly out of it. His hands were shaking.

Alphys came to a decision then and grabbed Toriel by the arm. She took her a few paces away from the brothers, who didn’t seem to notice them anyway. She kept her voice down regardless. “Toriel, I-I think I know what’s going on here. But I don’t know what we should do about it.”

“It’s okay Alphys, we’ll figure it out.”

“Y-you remember what I was just telling you about? B-before the brothers i-interrupted?”

“Yes. You were telling me about the souls Asgore has taken and the determination extractor in your lab.”

Alphys shook a bit from head to toe. “I had to tell someone… I can’t do these experiments anymore… I…” Toriel patted the nervous monster on the shoulder and smiled warmly at her. 

“It’s okay, Alphys. This is a safe place. There is no judging from me, okay? Tell me what we need to know.”

Alphys nodded, swallowed, and took a deep breath. “The brothers. They’ve been drugged. I… I recognize the symptoms.”

“Drugged?” Toriel put her hand to her mouth, as if the word hurt. Now, the scientist was gaining confidence and she continued, the words spilling from her in a torrent of exposition.

“Yeah well you see the machine. The determination extractor. There are all kinds of by products that it produces. A rare one is this serum.” She blushed and turned her head away. “I touched it once and it made me… it made me… extremely amorous. Undyne and I… for hours...”

“You’re saying they are…horny?” She blushed again.

Alphys nodded, concern in her face. “Extremely so. And it would appear as if they have ingested it. Perhaps even massive quantities of it. Diluted in food, it would have been tasteless. And Asgore has access to my lab and my notes. But why would he want to drug the skeleton brothers like this?”

Toriel sighed. She knew why. Sans and Papyrus? They were human. (How or why they had made their home in the underground and had no flesh… she and the brothers themselves, had no idea.) Thus, they were capable of producing half monster, half human hybrids whose souls were powerful enough to help break the barrier.   
Papyrus believed himself to be infertile. Toriel wasn’t so sure about that. (Papyrus maintained that the first time he met Undyne, during a Ceremony some years ago, she’d accidentally impaled him with her spear, permanently damaging him.)

Toriel sighed. “Well, at least they aren’t in any danger.”

“Oh no! No no no!” Alphys waved her hands. “The danger is very real! The serum? It’s more of a poison. If they don’t get the antidote, they’ll die!”

“Die?”

Alphys nodded. “From the state of them I’d estimate perhaps… an hour for Papyrus? Then he’ll most likely go into shock and his body will start shutting down.”

“Enough, Alphys. What’s the antidote?”

“Oh well, that’s easy I guess. Certain endorphins and hormones are released during the copulation process, so in theory they just need… intercourse.”

“Couldn’t they have just… taken care of it themselves?”

“I imagine Papyrus must have tried that at some point, which would explain why he’s missing his clothes but it’s not enough. The components introduced by a female participant may be essential for the antidote to take effect.”

Toriel pinched the bridge of her snout between her fingers. Asgore gave her no end of trouble. Alphys was wringing her hands so hard Toriel was surprised she hadn’t rubbed them down to the bone. The scientist was still going on about the scientific process, expressing her desire to help if only because the brothers were her friends and that she wouldn’t touch Sans seeing as how he was Toriel’s lover and gosh was she sorry she had been a part of this and…

The old goat held up a finger, stalling Alphys in her tirade. “No, Alphys. You can’t be involved in this.”

“I don’t understand. Why not? It would be much more efficient if we both helped. I could even call Undyne and…”

“I said no. Asgore knows that Sans and Papyrus are…” Alphys cocked her head, waiting for Toriel to finish. But she just sighed. Asgore, somehow, tricked the brothers into ingesting this serum that would make them so horny they would die without sex. Then he stuffed them into a room with a bunch of female monsters that had undoubtedly also been drugged, all in the hopes of breeding a couple of half-monster souls. This was playing out like a bad porno.

This went beyond the barrier. Asgore didn’t need so many souls just to break out of the underground, no. He obviously had greater ambitions at work here. She sighed. “We can’t risk you getting pregnant, Alphys. It doesn’t matter for me; I’m past my childbearing years.” For a moment, that brought on the pleasant memory of her last child, and the wonderful circumstances that had brought that child into the world. 

The brothers were weakening. They had very little energy left. But she would do anything for Sans and if she had to do this to keep Papyrus alive and spare Sans the loss of his brother, well, she would do what she had to in a heartbeat.

She turned to Alphys one last time. “I do need your help for something though. You said just a drop of the serum affected you for hours. The boys don’t have that kind of energy. I need you to go into my garden and collect snails. As much as you can find. Bring them back here. Then go out and get more. Can you do that?”

“Er, well yes. Of course.” With one more look at the incapacitated skeletons, she left.

Toriel turned to Sans, knelt down in front of him. He didn’t bother opening his eyes, but his hands clenched, like he was trying very hard to keep them to himself. All of his will was being used to fight the sexual impulses. He must have been terribly uncomfortable, his cock was straining against his shorts in a rather undignified way. “Listen to me, Sans.”

“Tori?”

“Yes. It’s me. I’m going to help you. You and your brother.”

He was quite for so long that Toriel thought he’d finally passed out or fallen asleep. “No.”

Toriel blinked, surprised. “Sans, what are you saying?”

His brows knit together, “No. Not like this. This? This is… it’s what _he_ wants. Asgore. Set me up _again._ I’m not… I’m not playing his game.”

Toriel took Sans’ head in her hands, he opened his eyes a crack, regarded her with an expression more serious that she’d ever seen. “My love, listen to me. We need to do this. That serum? Alphys…

“Alphys is here?”

“Focus, Sans! Alphys says that whatever you ingested is a poison. It will kill you unless…”

“Unless we bone? Hehe, that’s… that’s hilarious.”

“Your brother doesn’t have much time left. I’ll have to start with him.”

“You… you’re gonna have sex with Papyrus?”

Toriel looked across the couch where Papyrus lay, barely breathing, his ectoplasm cock hard even now. Toriel loved Sans, loved him more than he knew. If she could spare him the soul crushing sorrow of losing his brother, she would do so gladly.

Sans’ hands tightened over hers and he closed his eyes again. “I understand.” He relaxed a little. “I love you, Tori.” She leaned in close and kissed his forehead. “I love you too, my little snail.” Then she whispered, “Now just lie back and enjoy this experience.” He nodded, that grin of his widening.

Toriel striped off her clothes, folded them neatly on the coffee table. Alphys returned carrying a large bowl filled with snails from the garden. She made a little squeak when she saw Toriel naked but otherwise did a decent job of hiding her discomfort. She snatched up a snail, violently sucked the little creature out of its shell and straddled Papyrus. She tilted his chin up, he did not resist. Forcing his mouth open with her tongue, she slipped the snail from her mouth to his.

She felt him swallow. The snail was slimy and slid down easily; its taste was not unpleasant. The snail was pure protein, within moments, Papyrus’ breathing was stronger, he groaned. Toriel snatched another snail, sucked it out. This time when she lifted Papyrus’ chin his mouth opened on its own. His tongue, warm and wet and vibrant orange, snaked between her lips, filled her mouth and took the snail.

When Papyrus had swallowed again, Tori glanced at Sans to see him reaching weakly for the bowl.

“Ugh,” he groaned. “I can’t reach. Feed me?”

She grinned, popped a snail in her mouth and stood above Sans, her hands tipping his chin straight up the same way she had done for his brother. Groggily but happily, he gazed back at her.

“You want this?”

“I want it.” His hands crept over her thighs, gripped weakly at her hips.

Instead she swallowed. “You’ll have to wait your turn.” He could only watch as she dropped to her knees in front of his brother.

Alphys stood off to the side, not wanting to watch, unable to turn away.

Papyrus’ cock was ready to go, had been ready for hours, but for Toriel it wasn’t enough just yet. Sans watched without shame as she slipped her mouth around his brother’s shaft, slowly fitting it all inside of her. Her tongue lapped at it, making it slick. To her own surprise, she felt herself getting wet. Papyrus tasted good.

Sweet, like candy.

“O-oh dear.” Muttered Alphys, positive no one was listening to her. “It is possible there may be some transfer of the serum through skin contact.”

She almost couldn’t stop. Toriel could feel his dick twitch and pulse, he was ready to cum but it seemed this wasn’t the stimulation that would finish the job. It seemed the serum affected its victims in a very particular way.

Sans; wonderful and ever anticipating her needs suddenly thrust his tongue between her thighs. What a sight they must have been, a cascading couch waterfall of bodies. Paps at the top, nearly unconscious, his legs spread wide; Toriel, between those legs and lapping at his cock like she was dying of thirst and sans, his face buried between her now dripping legs. Toriel’s breath became shallower, her cheeks were burning. Sans’s tongue was slipping between the lips of her fleshy mound. Somehow, he had gotten a hold of the bowl of snails and glutton that he was, had eaten them all.

Alphys did her duty, when Sans had left nothing but shells in the bowl of snails, she ran out to the garden to get more. When she returned, it was just in time to see Toriel position herself over top of Papyrus. Sans watched, his own cheeks flushed blue, drinking in the sight, as Tori placed Pap’s cock against her wet pussy. She took one last look at Sans.

He smiled lustily at her. “Go ahead, baby. Make him squirm.”

Alphys hid her face in her hands but peaked through her fingers, her knees shaking.

Tori closed her eyes and slowly thrust downwards. Papyrus slid inside of her, hot and hard but soft and filling. She gasped. San’s stripped off his shorts, not sure how long he’d be able to last just watching. Papyrus shuddered as Toriel came to rest against his pelvis, his tongue slid free of his jaws, his breathing stronger. Toriel was filled, could feel Pap’s tip pressing against her cervix and for a moment, she couldn’t move, stunned to stillness by the sheer feeling. She felt a rush of headiness. The serum, transferred from Papyrus, flooded her system. Conscious thought began to shut down, replaced only by base instinct.

She began to move, it didn’t take long. He was so pent up; wound so tight, that after two thrusts Papyrus convulsed. His back arched, his pelvis thrust upward, his eyes opened as he spewed vast amounts of cum inside of her. Bright orange and glowing, it squirted everywhere, seeping out from Toriel to slip down Pap’s cock and across the couch.  
Toriel gasped in pleasure. There was no change in Papyrus even as he emptied his load inside of her. His cock remained hard.

“Holy shit,” muttered Sans, feeling hot and stripping off the rest of his clothes. Undaunted, Toriel continued to thrust.

Papyrus had a moment of clarity, “Toriel?” he mumbled, his eyes still half closed.

“It’s me, Papyrus. Don’t worry, you’re safe. Let go.”

“Yes, Ma’am.”

Grabbed by a fever, strength returning, he clutched Tori at the hips and began to thrust on his own. Tori made a loud noise in the back of her throat, earthly and primal.

It was all too much for Sans, he could wait no longer. He climbed atop Tori, who didn’t seem to notice until he whispered in her ear. “I can’t take it anymore, Tori. Seeing my brother’s cock inside you… I… I’m joining in.”

Her gaze was glassy, her will crumbling much faster than either of the brother’s. “F-fill me,” she panted. “Fill me!”

Sans wasted no more time. His cock, bright blue and throbbing, pressed against Tori’s ass. With a cry, he shoved it home, hearing a moan from his brother as the extra fill pressed against his member, making Tori’s pussy tighter. 

The three of them came together; Toriel screamed, Sans swore and Papyrus Nyeh’d. Cum, blue and orange, spurted across the three of them.

Alphys fumbled with her phone, hands shaking so bad she could barely dial.

“Alphys?” came Undyne’s voice from the other line, “You’re calling me? Are you all right, what’s wrong?”

“I need you, right now!”

“What? Alphys I just dropped by your place, you’re not even home. Where are you?”

“At the ruins…”

“You’re visiting the old goat?”

“P-please! I’ll explain when you get here just… come quickly!” She terminated the call, hoping the urgency in her voice would translate through the call and speed Undyne on her way. Alphys watched the trio without shame now, she was beyond that.

Papyrus had turned Tori onto her side, her one leg held high in his grasp so that both brothers could still reach her. She was drooling; her eyes were nearly rolled up into her skull as the skeletons thrust at her two openings in tandem. Papyrus came yet again, Toriel felt her belly swell, Sans was only a few strokes behind filling her ass with his cum.

Alphys shook. Small droplets of womanly lust hit the floor between her feet. Maybe… Maybe the serum was affecting her through… proximity? Yes. That must be it.

Suddenly, Papyrus pushed away from Toriel, positioned her so that she was on her knees again, bent over the couch, her legs spread. Sans teleported beneath her, they had switched places.

“S-scream for me, babe,” whispered Sans as he shoved his hard blue cock deep into his lover’s pussy. And she did, she screamed, her tongue hanging out of her mouth. Then Papyrus thrust hard into her anus and she screamed again. 

Undyne came up the stairs at a run, heading for the screams. She wasn’t sure what she would come across when she flung open the door to the living room but… it certainly wasn’t this. She stared in shock, taking in the three writhing bodies on the couch and Alphys, writhing in her own way off in a corner, flushed and shaking.

Unlike the others, Undyne had no reservations about what might be going on here. “Oh, hell yes!” she grinned. She stripped off her jacket and tossed it aside, she didn’t care where it landed. Alphys saw her, reached out to her, but seemed unable to move. Undyne had no problem taking control. She grabbed two fistfuls of Alphys’ jacket and tore it free, revealing the shaking dino-scientist beneath.

“I don’t know what’s going on here,” she said as she forced Alphys to her knees on the opposite side of the coffee table, her front pressed hard against the glass. “But we’re going to _watch_ every moment of it.”

Excitement spilled through Undyne’s system, her stomach turned to butterflies, but her hands never shook. Alphys moaned.

“Oh yeah,” said Undyne. “You like what you see, don’t you?” She lifted Alphys tail, the woman shuddered. Then Undyne plunged two fingers deep into her pussy. She was more wet and slippery than Undyne had ever felt before. It drover her crazy, her grin widened.

The other three hardly noticed but the added noises only seemed to increase their ferocity. When Toriel looked down, she could see Sans beneath her thrusting, her breasts swinging in his face, his hands gripping her hard and fierce. His tongue lolled out of his mouth, he seemed to have no control over it. It occurred to her that the same could be said of both herself and Papyrus who was dripping saliva across her back.

Undyne flipped Alphys over, lifted her thighs. Her head hung just over the edge of the coffee table, where she could see every little thrust and shiver from the trio in front of them. Thin as she was, Undyne was strong (and hoped the coffee table would hold their weight) as she forced Alphys into a mating press, pressing her own dripping vagina against hers.

She pressed hard, squishing her own clitoris against Alphys’, who gasped, her blush spreading from her checks to her chest, loving the feeling of being all compressed together, Undyne thrusting on top of her, grinding their parts together. Wet, slippery sounds escaped from between them.

The hours began to pass. Alphys and Undyne were the first to give up, as neither of them had gotten a dose of the serum. They slumbered peacefully and satisfied on the floor, wrapped in each other’s arms. Somehow, the trio found their way into the bedroom, where they would be more comfortable. The night became a blur of body fluids and orgasms. 

Toriel’s mind was numbing, she stroked whatever she could reach and sucked whatever came near her mouth. Her body moved of its own accord, someone would cum but no one would stop. She began to remember only pieces of the night. They experimented, moving around the bedroom. The bed, the dresser, the night stand, the floor . Any thought of the serum and antidote no longer made sense; they simply experienced each other with no reservations or inhibitions.

Toriel was next to pass out. Exhaustion over took her.

The boys weren’t done though. They continued to use Toriel’s body, forcefully but gently moving her into whatever position they needed. Sans gave out sometime later; that grin on his face seeming satisfied at last. Papyrus continued far longer than any of them, displaying a stamina that would have astounded either of the other two if they had been awake to witness it. 

  
The next morning, when Toriel woke, she felt pleasantly sore. Memory flooded back to her in waves. She had that morning after feeling of needing a shower but not really minding it. Sans slept soundly beside her, nestled into the crook of her arm. Papyrus was not there.

Worried, slipping out of the bedroom with a housecoat and tiptoeing past the two snoring lesbians, Toriel went in search of the missing brother.

It didn’t take her long. Papyrus, naked but for a sheet draped around his shoulders, sat on the steps of the ruins, his breath misting on the cool morning air, a cup of tea (plus a teapot and extra cups beside him) steaming in his lap.

He didn’t look at her when she sat down next to him.

Toriel poured herself a cup of tea. “Are you alright?”

“Nyeh.” 

She waited patiently. There was time now. Eventually he spoke. “Toriel, I… I’m so ashamed of how I acted last night I…” She stopped him with a light touch on his shoulder. He leaned into it a bit, grateful for the familiar contact.

“There is nothing to be ashamed of, Papyrus. There was an issue, we took care of it. That’s all.”

Papyrus stared at his tea. She said those words but he recalled the moment he came back to himself. The moment he _could_ have stopped, but didn’t. Toriel passed out, Sans snuggled up to her breast, the both of them looking happy and contented. And him. Taking advantage. He could still feel the way her pussy felt against his cock, and he gave a little cough, lest he get aroused again.

“I… I remember doing things… a lot of things. It’s not even Ceremony season.”

Toriel smiled. “It wasn’t your fault, Papyrus. Asgore did a horrible thing. I don’t think he anticipated your strength of character. Neither you nor your brother gave in to those… urges… and I am honoured that I was here to help.”

Papyrus nodded, smiled and slurped his tea. He took a deep breath… and let it all out again. This incident wouldn’t change them. If anything it would just bring them all closer together.

Suddenly, Toriel giggled. Sans materialized right in her lap, his hoodie draped over his shoulders. He was smiling a genuine smile. He said nothing, he didn’t have to. Toriel wrapped her arms around him and held him close, happy that he was also alright.

Alphys snuck through the door, trying to make as little noise as possible. She sat beside the three, who looked at her curiously. Her white scientist jacket was enfolded around her like a blanket. She sat beside them with a blush, but said nothing. The trio was unsure what to think, afraid that they had somehow included Alphys in their fevered lovemaking,

The door banged open yet again, all four of them jumped. Undyne was as naked as the day she was born, her toothy grin wide and pleased with herself. She sat down next to them, not ashamed or embarrassed. Together they watched the glow over the horizon, the only indication that it was dawn in the underground. 

Sans finally broke the silence. “Undyne, why are you so happy?”

“Heh.” She examined her fingernails. “I got me some.”


End file.
